Since the VMS linker distinguishes symbols based only on the first 31 characters
of their names, it is occasionally necessary to shorten symbol names in order
to avoid collisions. (This is especially true of names generated by xsubpp,
since prefixes generated by nested package names can become quite long.)
"ExtUtils::XSSymSet" provides functions to
shorten names in a consistent fashion, and to track a set of names to insure
that each is unique. While designed with xsubpp in mind, it may be used
with any set of strings.

This package supplies the following functions, all of which should
be called as methods.

new([$maxlen[,$silent]])

Creates an empty "ExtUtils::XSSymset"
set of symbols. This function may be called as a static method or via an
existing object. If $maxlen or
$silent are specified, they are used as the
defaults for maximum name length and warning behavior in future calls to
addsym() or trimsym() via this object. If the compiler has
been instructed to do its own symbol shortening via
$Config{'useshortenedsymbols'}, a value of 2048 is
assumed for $maxlen as a way of bypassing the
shortening done by this module.

addsym($name[,$maxlen[,$silent]])

Creates a symbol name from $name, using the
methods described under trimsym(), which is unique in this set of
symbols, and returns the new name. $name and its
resultant are added to the set, and any future calls to addsym()
specifying the same $name will return the same
result, regardless of the value of $maxlen
specified. Unless $silent is true, warnings are
output if $name had to be trimmed or changed in
order to avoid collision with an existing symbol name.
$maxlen and $silent
default to the values specified when this set of symbols was created. This
method must be called via an existing object.

trimsym($name[,$maxlen[,$silent]])

Creates a symbol name $maxlen or fewer characters
long from $name and returns it. If
$name is too long, it first tries to shorten it by
removing duplicate characters, then by periodically removing
non-underscore characters, and finally, if necessary, by periodically
removing characters of any type. $maxlen defaults
to 31. Unless $silent is true, a warning is output
if $name is altered in any way. This function may
be called either as a static method or via an existing object, but in the
latter case no check is made to insure that the resulting name is unique
in the set of symbols. If the compiler has been instructed to do its own
symbol shortening via
$Config{'useshortenedsymbols'}, a value of 2048 is
assumed for $maxlen as a way of bypassing the
shortening done by this module.

delsym($name)

Removes $name from the set of symbols, where
$name is the original symbol name passed
previously to addsym(). If $name existed in
the set of symbols, returns its "trimmed" equivalent, otherwise
returns "undef". This method must be
called via an existing object.

get_orig($trimmed)

Returns the original name which was trimmed to
$trimmed by a previous call to addsym(), or
"undef" if
$trimmed does not correspond to a member of this
set of symbols. This method must be called via an existing object.

get_trimmed($name)

Returns the trimmed name which was generated from
$name by a previous call to addsym(), or
"undef" if $name
is not a member of this set of symbols. This method must be called via an
existing object.

all_orig()

Returns a list containing all of the original symbol names from this
set.

all_trimmed()

Returns a list containing all of the trimmed symbol names from this
set.